(Field of the Invention)
The present invention relates to an annular type gas turbine combustor of a kind having a plurality of fuel nozzle assemblies disposed on a circumference (or in a round row).
(Description of Related Art)
In recent years, in the light of the pressing environmental concerns, the reduction of noxious substances such as, for example, NOx (nitrogen oxides) emitted from gas turbines is increasingly demanded and, in order to meet with this demand, development of a lean combustor have now been taken place. The lean combustor is of a type capable of forming a leaned air-fuel mixture by allowing half or more of the air, then flowing into the combustor, to flow through fuel nozzle assemblies. As leaned fuel nozzle assemblies of the lean combustor, concentric fuel nozzle assemblies are used in which combustion takes place at all of operating points, including ignition by means of pilot fuel nozzle assembly disposed at a center portion of the leaned fuel nozzle assemblies, and a low NOx combustion is accomplished by a main fuel nozzle assembly, disposed radial outside of the pilot fuel nozzle assembly, at an output exceeding an intermediate output. In this respect, see the patent document 1 listed below.
In general, ignition in the combustor takes place in the following sequence. At the outset, a spark of an ignition plug is captured into a circulation region formed downstream of one of the fuel nozzle assemblies to thereby form a flash point. Then, the flash point is propagated within the circulation region in an upstream direction and such one of the fuel nozzle assemblies is ignited to form a flame within the circulation region. Thereafter, the flame is propagated to a circulation region formed downstream of the neighboring fuel nozzle assembly. The flame is propagated to all of the fuel nozzle assemblies and the ignition completes with the flame stabilized and maintained.